Keying



Oct; 16, 1934.

G. E. PRAY KEYING s Sheets-Sheet 1 Filed NOV. 19 v 1930 ESE:

INVENTOR G.E P Y BY ML/ ATTORNEY Oct. 16, 1934. G, E PRAY 1,977,596

' KEYING Filed Nov. 19, 1950 s SheetsSheet 2 1 T Aw INVENTOR ATTbRNEY Oct 16, 1934 a E P 7 1,977,596

KEYING Filed Nov. 19, 1930 3 Sheets-Sheet 3 INVENTOR G. E. P Y

I. vf/l/ ATTORNEY V I ni -Em o r jYe llelive yNs 11. 159; i

- signer. to BadioiCorpo notation ofnelavvaitef en were;

- pplication Nmwmbei-zsi,imimseirnuis;niaeiaz-v z a 1 inYentionfiielates totransniitters and in particular "to a no vel method of and means, for] e n tra smit er in l din 1 thqdtp an means" for ':e 1iminatingj key shocks. heretofore 1 P es nt in tra mi e s- .1. i It is. w'el1 knownjthat when a radio receiver or radiojreceiving equipment is mounteddn the vieinity of a transmitterthe reception of signals in said'receiver is interfered with more or iles's by disturbances originating in the transmitter; In eachj tkeying'nqpl'ation of the transmitter the rise'and fall of the'signall currentin "the circuits thereof is audible in a receiver, adjacentthereto int he' forin o'f a cracking noise known injthe' the transmitter fis- 't9 the receiver the "giieat'erjis he .'in f i u ed b t e e smme iin the i-eceivedsignals. lithe transmitter islooate'd in the" same room or vclose 'to' the receiver i then reception of signals in the'zrecjeiver becomes pracj: wi y-im o d ng th time in when th transmitter is operating;

Attempts have been rnade heretoforeto m l i tu b c i reee f s c r its h originatein' a transmitteriocated. adjacent there: to.,.f One method used heretoto're to eliminate such disturbances in the receivers involves the use of shielding. f or thereceiver and/or for. the transmitter. Another method oontemplatesfthe' use iof'radio frequency choke coils in the receiver and/ or. transmitter oirou'its; Generally ,such flat tempts have been-more or less unsuccessful. due to the fact that 'when'th e firstl methodisjused the: shielding 'efieetis .not completefand when the second method: is oom'plete elimination isnot obtained sincethe initial stageroi the oscillations in the transmitter due, keying eon} tains a practically continuous frequency band or; spectrum; Choke coils used for this purpose would block out-a singie frequency oriar narrow band of-f-requencies; Oscillationsof other free qun'cieswould enter the'radio. receiving circuits and' causedisturbances .thereing'. t; 1. The' o'bjec't of th'e present; invention is'to'brovide a n'ovel'xnethod- 'of and means for'eiimina'tin'g at the source, tliat is in the transmitter; disturbances which ma afie'c't radio receiving Qpp'aratus and which are due to-keyingbpera' tions of the transmitter; f Another object of" the present 11nvenuqn' istq provideanovel method) or and. means for felin i nat'i fi's',"k yi t ifitl li m tla h ul: is in I the transmitter, in 'yv hichhthe Lke'y'ing 2mm i eee ia mwlea fia i- We e 5 1 5 ke v c c N k y. sheen, l' Th ynear r;

-pm): a

disturbancesto 15$ 'elir nin,a'ted,l arefof lowfarnplitude,- Hu mu e h rbbie l rwm .b come a p from areading q f thespeielt iezii'li. 0'11, v

Briefly andbroadlythe above objects are obm tained by the; usejof 'ajjkeying system for, trans: n itters' which includes mjeans'xto' prevent the suddenvrising of the ke'yingcurrent at the start of fke'ying operation and the abrupt falling off thereof at the termination ot the keying opera tion jnfrhisin lzey signals, the sharp edges 91 .which'are;ja s it were roundedofl; h In one n odi ficationfoilthe invention the keyingJnieans'inYQIVIes-the use of a keying tube "havin'gits anode-con e'tedfto the screen grid eleotrade t n; ub esjin i the" high frequency generator. it inputjfloirouit@connected in a neve g ah tea s ur e 9 e ial hr u h at t' i lw ik; i h t f l ni jwh eh a e r m-W idned'} to retard a change "in the input current dur lto suaaenehan 'es, oi. qteiim i; on the imme th ying tube and consequently reand finaljjchangeslinthe"keying 'en'tial appearing on the anode of r i' r Said ikeying'tuhe; t 7 [A {Iurthehhiodifieation involves an arrangement which thein'put circuit oi! the keying tube' including the .filter network is somewhat similar te-theinput circuitandhlter network of the keying'fiubefdescribedi above but in which the anode circuit or the keying tube isco'nneoted tov the anode. circuit of; one, or the tubes 1 of the transmitter in sueh i'a manner that. the keying potentials, the

tco 'rner's ol whichare. rounded off as hereinbefore i ideseitihed, are applied to the anodeof said transmittnihiodulate the frequencies generated or v V Inthe abofvedesoribedmodifications the key mg potential for the input of, the keyingtube is ohtained'byithei useiot a battery having opposed terminals connected together and," to the filament or the-keying tube whilefl the' other terminals thereoi are connected to oontactscooperating with the key in such a manner that negative and .positivebotentials' 'Iiiayhe alternatel 'applled'tothe .amblified', therein.

controlfeleetrlip li, I'Qf the keying tube;

,Stillanother arrangement'is provided wherein the vlteyin'gliinpulses which areapplied to the control electrode of, one of the; transmitter tubes, are obtained by a keying tube, the input circuit of which connected. with 'alres'istancejsllDDhed with potential from any, source, which'j resistance supplies the anode cathode and control electrode potential for the keying tubegand the control electrodepotential iorth "transmitter tube. A-second following detailed description thereof and there: w from when read in connection with the attached drawings throughout which like reference numer als indicate like parts.

Figure 1 shows one embodimentf f applicarlts: novel keying means and its application toa-transmitter;

rangement of Figure 1;

Figure 3a shows novel means whereby'tlie ar rangement cf,Figure 3,- may be energized by a single source; while Figure 4 shows curves characteristic of the currents flowing in certain o eslor. the circuits of @119 hereinbefore described arrangementgj," r [Q Referring tothe drawings and in particular to Figure 1 thereof, 1 is a thermi'onicfamplifier or os-' cillation generator'having its input circuit 2 0011 nected to a source of 'oscillation'3 and its output tank circuit 4lconnectedtoaload circuit 5. The oscillation generator or amplifier in itself 1 forms no part of the presentinvention. A detailedde? scription thereof is seemed; unnecessary except to state that the frequency of the input circuit 2 y b fi n b he i QaPQF Y ShOWII therein while'the output. circuit of 1 incluq'flsfi blocking condenserffi', and a ,tuined tank ci'rcuitf i, as shown. Potential is supplied to th scre en grid and the anode ofthermionic tube '1 fiZQIf fa'sQui'ce B'+ c(not shown) through resistanceR handchoke coil H respectively. Thepurpos'e ofresistanceRg is. to' reduce. the potential jreaching' screen grid 7 while j the purpose' of 1 the choke; coil H is tc' prevent high frequency oscillations appearing on the anode'of 1 from reachingthe sou'rc B-i-L f In order thatthe oscillations appearing in the anode circuit of 1 maybe ,lxnodulatedat signal frequency the screen grid electrode '7 of tub e'1 i's connected to the anodefi of thekeyingtub'e'p in such a manner that potential frornj Bthrough 13;: supplies the anodecathode circuit oftubeQQ fa's' well as the screen grid 7 of tubejl. The pbtenf tial of the anode 8 and the direct current 'iiowe ing in the anode cathode circuitof tube 9 willvary atsignal frequencyjasiwill appear in detail'her inafterl This variation will be utilized tofkey thermionic tube 1. The variations will start and terminate slowly in accordance with thepresent invention, thereby eliminating keyf clickslhereto fore present in transmitters of thi's typ'ei In' orderthat the potential appearin aliBfajnd the current flowingin the anode circuit of 9 they vary at signal. frequency the input circuit 1Q of tube, 9 includes'ia key'K'adap to connect the grid 111 of tube 9 throu h aires sten jiaf'ither to the negative or positiveterrninalof battery E,

the midpoint of whichi's connected, sfi'ridicated; to. the filamentsofstubesill;and 9, whereby mani ulation: of the'key K will applyfto the grid 11f a potential either negative or positive lwithirespect 1 to t e filament-of thetube'Q; 'wn iijt'h ek -r;

n s he gridllef. 'i ne a ve term na of battery E the tube 9"is nonconductingand since no current can flow 'betweenthe anode 8 of tube 9 andthefcathod'e ahigh potential is applied to the screen grid '7 of"tube1".*Thls is due to the fact that the anode cathode circuit of tube 9 and the screen grid cathode circuit of tube 1 are supplied with direct current through a common circuit R2, B+. When the control grid of tube 9 is connected to the positive terminal of the a e ub 9 be es. qon u ive and .a d cathode k'nlirrentjflows therein; "Ihisabsorbs current from the screen grid cathode circuitof tube -l-. This tends to decrease the potential at '7.

I Up to this point applicant has described a novel and efiicient keying method in which rer-verse keying is obtained and in which keying shocks and key clicks are substantially reduced due'f't o the inherent'characteristics of the circuit. Ho vlvevler;order; tofurther insure that the keying potentials on the anode 8 do not rise and fall azat too rapid arate the electrical inertia is applied in accordance with the present invention to the input 'circuit of tube 9 and to the output circuit thereof in .theform 9 a resistancev R1, a condenser C1,, a resistance 3: and; a condenser" .02, InIia'ctual'practicejit has been found that the condenserCiinay, and often does, comprise'the capacity between the control' elec'trode' and cathode, of tube 9.. Filament heating -current is sup plied 'to .tliec'filanients'io'f jtubes l and' 9 frontai l monisourcejof po ent al; A, .as 1shown, while "egauveflpctentim issupphefd to] the grid "or-*1 from a source'G.]j -l' E l f f I izzrhearr n m n shownin F u zg s me: whatgsimilar" to the, arrangement. or Figure 1f. Th iiar aj i em tlO ..J ig r diffe mmthe arrangement [of Figure 1 in several re pects. In Fi ure Z'Lh q l a h d im i i pt Si derives its current and potential, from" the same circuit; which supplies current 'andipoter'itial to the anode and cathode circuit of tube 1, thereby prod j a dde'f du etio a 's e'r'ial f e uency; which reversed with respect to fltheij keying 'op erations while the inertiajnece'ssary to round off the sharp corners of the' keying modulation is obtained by resistance Rifc'ondenser Cifan'd reof n ii fter; l t e f rr'angernent of Figure 3 s fl ovid j In: t is 'rr n m t the tiiasin notei al qr he li qli elec od of tt ibj 1,, ndthe anode potentiallandfthe controlgrid elec rode t'ential' for the I ngtube Q'are'sup} plied; fro single resistance, which may. be p011:

e 't dacross n source (qt ec cur n potential 'j LV. jfIfh'e anode cathode and screen grid eathode potential for the ampliiier'l is supplied from 'a'separate high voltage source In this arrangement the potential offthe comm e trode -12' of tube"1'is'-deterinined by the current which 'fl'o'wsj in the anode-cathode 'circuit 'of "the keying tube- 9 "since theanode 'cathode current i-n 'th'e tube 9 is made upof the-rectified .current in ther'grid cathode -circuit'of ,1 and of-the current :due etc the'.voltage-;- dropped across R When the key Kzsupplies"az negative potential to ,thecontrol-ugrid 111 through R1 the tube 9-is nonconducting rand since, no, 7 current can. flow in-the anode cathode; :cirouit thereof the poten-a tial applied to. 12 ;is negative, thatianore nega; tive thannormal, and the oscillations generated or amplified in 1 are cutoff vWhen ,thekey K connects the control gridffl l to apos itive point its ilc

potential applied to=the"gr'id 12 of tube 1to' become less negative, making the tube conductive, and allowing current to'fiow in theanode cathode circuit-thereof. In this modification the keying operation is simultaneous in the keying and in the keyed circuits; The current in the radio frequency circuit, that is, the output circuit of tube 1, will follow the same curves asthat'of the keying circuit 10 and inthe input circuit of the keying tube 9. In theapparatus, as arranged in accordance with applicants novel invention shown in Figure 3, the current flowing inithe output-of 8 and in the input circuit of 1 will lag the keying operations due to the inherent nature of the circuits. This in itself will tend to round off the corners'of' the keying current, thereby eliminating key shocks and key. clicks from being produced by the circuits. In order to further insure that the current due to keying. does not rise or fall too rapidly additional time lag characteristics are obtained'by providing additional inertia in the form 'of resistance R1, condenser C1 and resistance Riand condenser C1. The condensers 15 and 16 tend to eliminate any potential variations appearing in R4 at audio frequency 'and preventing such variations from affecting the signals to be transmitted. It will be noted in this modification that separate sources of potential. are required for the filaments of 1 and 9 in order that the keying currents therein be confined to the proper circuits so that the anode cathode circuit of tube 9 will-carry the rectified current flowing in the grid cathode circuit of 1 in addition. to'current flowing therein due to potentialdrop across resistance R4.

In Figure 3a is shown a keying arrangement which may be applied-to the input circuit of keying tube 9 and .which permits the use of a single source of potential to operate both tubes. In this arrangement, the potential necessary for the entire operation of the apparatus including the radio frequency tubes and. the keying tube 9 is obtained from aresistance R4, R5 adapted to be connected across a source of high potential HV not shown. Keying potential for the control grid 11 of keying tube 9 is supplied through a resistance R1 connecting said gridfwhen the keying K is in the open-position to the negative terminal of the resistance R1 and when the key K is close to a predetermined point on R4, which is positive with respect to the negative terminal of R1. In this manner the keying tube 9 can be rendered conductive or nonconductive by manipulation of the key K1. The control electrode of radio frequency tube 1 is connected as in Figure 3 to a point on resistance R1 so that the potential applied to the grid 12 of 1 may be varied at signal frequency in a manner somewhat similar to that in which it is varied in the modification shown in Figure 3; 1 In this arrangement manipulation of K1 varies the bias applied to the grids of tubes 9 and 1 between the limits of some predetermined negative values of voltage. The anode'cathode current flowing in the keying tube 9 is, as in Figure 3, the sumof the rectified grid current flowing in tube 7 and the current flowing due to the potential drop across R4. Since the current which could flow in the anode cathode circuit of the keying tube 9 depends on the conductivity of the tube the potential applied to the grid 12 will depend upon the position of key K1. It will be noted in this modification that the keying tube 9 carries a large portion of the anode cathode current for the radio frequency tube. This condition occurs due to the fact that keying tube 9 'oifersi-a relatively low resistance path for the return of anode cathode current. from the cathode of tube 1 to the negative side of the high voltage. This results in no serious disadvantage butdoes result in a change'in the form of the keying wave .f

"In connection with Figures 1 and 2, it will be understood that although separate sources of potential have been shown to energize theelements of the several tubes, all: of the elements of the tubes may be energized from a single source. In the arrangements'of'Figures'3 and 3a, separate sources of potential are used for the fila ment'softubesland9k' M Inexplainingthe'operation' of the several modifications reference will be had to Figure 4 of the drawings i'n'whi'chcurves are shown representative of the current flowing in various cir-- cuits of the tubes plotted with reference to time. The operation of the keying circuits shown'in Figures 1, 2 and 3 is the same,-and a. statement of the'operation of Figure 1 will be sufficient to explain the operationof all 'of' these modifications. Referring to Figures l, 2and'3, and the curves of Figure 4, assume that the keying relay K connects-the negative terminal of the battery E to the grid 11 of keying tube 9 so that a; sufficiently negative voltage is supplied to the grid 11 ofkeying tube 9 to prevent the flow of any current between the anode and cathode of 9. If the grid bias could now be varied as a straight line to theproper positive value, as indicated by the dotted line Egig'curvea of Figure 4, the anode cathode current of 9 "would then follow the curved dotted line 'Ip as shown by the dotted line in curve' b of Figure 4." No practical scheme, however, has'yet been devised'to permit variation of the grid bias in a straight line to obtain the desirable result indicated in curve b of Figure 4. The next'best solution which has been devised in accordance with the present invention is to use filter circuits to introduce sufficient lag in the circuits to accomplish the above result. These circuits have been found to give very good results. While the keying relay K is in the positionindicated above C1 receives a negative charge. "If the'relay K now'moves to its other position wherein the battery E'tends to apply a positive'potential to the grid 11;C1 starts to discharge through R1 and after it has discharged starts to charge positively through R1 and then the grid 11 receives a positive bias. The grid-voltage curve obtained by the-use of this filter network is shown by the full line curve Eg position" connecting the grid 11 throughre-.

sistance R1 to the negative terminal'of battery E, C1 discharges through the tube and through R1 and then charges f negatively through R1 and allows the grid 11 of tube'9'to-receive a negative bias. The curve Eg of C shows the fall of potential of the grid 11 of-tube 9 when K connects said grid to the negative terminal of the battery E, which would result if the potential could be caused to fall as a straight line. The actual fall of the current on the grid Ea, as obtained by the use of applicants filter network or lag introducing circuit, is shown by the full line curve E9 of curve C of Figure 4. The anode cathode current which would appear in the output circuit of tube 9 if the potential on the grid thereof could be controlled in accordance with 1 connected with the. input electrodes of said sec;

E'g of curve'fC,: isindicated at Izroi'curve dict Figure 4, while the current actually obtainedin the' 'anode cathode. circuit of ;-tube.9 is' indicate bythe full line Ip incurved of Figure4k zzi 1 Inthe arrangement shownin..Figure:l3a;,.,the keying relay K varies the bias on grid 11 between the limits or" some predetermined negativevalues of voltage. limiting the maximumf value .of' lg) to somepoint on the straight line portion of the Igor-curves. This reduces the; time factor due to the upper portion oflp of curve 1) of Figure band causes this curve 1 .toafiatten. out sooner, thereby giving lowertmaximum but more abrupt curves at the top corners of the keying wave. ThlSjSQlik: wise a characteristicto a- ,lesser; extent of ;the modification shown in Figures 1,-2-and:3, especially-if -the keying relays were to; be replaced by one similar to K of Figure'3a. r

-Having-now described my inventionandthe operation thereof, ;what' I ,desire to protect by Letters Patent is: c, 1- i :LSignalling means-comprising a thermionic tube .having input and output circuitstuned to radio frequency], oscillations; a circuit, for modw lating-I said oscillations at signal; frequency including'a second thermionic tubehaving its output electrodes connected in serieswith' the-output electrodes .in said-first namedtube and-in parallel with a common potential source, a circuit ondnamed tube and adapted to vary the internal impedance :of saidtube-.,at signal frequency, wherebythe-- energy" taken; from said common source by said last named-tube ,variesat signal i frequency,v and acapacitive; impedance and a resistance in said circuit wherebyrsaid variations impedance of said tube at signal frequency are gradual. 1

2. In combination a high frequency thermionic tube relay and athermionic modulatlator tube 3. :The combination as recited finzclaim iin Which the thermionicrelay is of the screen grid type and in which the-screen grid toxcathode impedance of said tube-is connectedin parallel with the anode to cathode impedance of said tube. 4. Signalling means comprising,- a high fre quency relay circuit including a thermionic tube of the screen gridtype, meansfonapplying oscillations to be relayed to the input circuit of said i tube and arepeater circuitconnected with the anode of said tube, a connectionbetween vthe anode of said tube and the positive terminal or a source ofpotentia-L-a resistanceconnecting the positive terminal of said source to: the, screen grid electrode. of said-tube,,-a modulating tube mamas having vits anode t0 cathode impedance connected in. S1llllltrtc v the screeng-rid to cathode impedance of,saidrelay.tube, anda source of modulating pot.entia1s;-, connected. by; .a filter circuit with the input. electrodes of, said qmoduilating tube for varying the; impedance of, said modulating ,tube atsignal freguency.

-=5.S ignalling means comprising, a high frequency relay'circuit :including a-thermionic tube of ,the screen grid type,-.means for applying oscil lat-ions torbe 'relayedtothe input circuit of said tube and a -repeater-- circuit connected with ;the anode of said tube, a .connectionbetween the anode of: said. tubeyand the positive terminal of a'sourceof potential, a resistance connecting the positive terminal of-said sourc'eto the screen grid electrode of said tube, a keying tube having its anode to vcathode impedanceconnected in shunt to the; screen" grid t'o-cathode impedance of said relay tube, ,asource ofsignal potential, and a filter-circuit including a capacity. and a resistance connecting-.said-source of signal potential to the input-electrodes of said keying tube. 16.1High frequency.relayingv and modulating means comprising; a thermionic tube of thescreen grid type, :means for impressing high frequency oscillations to be repeated. on said tubecompris ing,; an inductance and-a variable capacity connecting: the control electrodes 'of said tube tonthe cathodeofr said tube, a circuit adapted torepeat :the oscillations relayed in said tube com,- prising, an inductance andxa capacity connected between/the anode and cathodetof said .tube, a keying tube having its cathode "connected tothe cathode "on saidcfirstjnamed' tube and its anode connectedto the screen grid electrode of said first namedfltube. by: way of azresist'ance and to the anode: of said firstcn'amed-tube by .way of an inductance meanswfor-connecting said resistance and said" inductance 7' .to the positive terminal of a sourceof potential, a capacity connected between the control grid electrode and cathode ofsaid key lug-tube, and a sourceofpotential and a resistance connected. by wayof a key-in parallel with said capacity. I I

"7-;In. combination, with1,a high frequency thermionic ,tuberel'ay and a thermionicmodue latingtube, acircuit connecting the anode to. cathode impedance-of. said modulating tube in series with theanode to: cathode impedance of said relay tube, said tube impedances being connected in parallel with a commonsource of potential, a;-'keying circuit connected with the input electrodes of said modulating tube, and a circuit and ,theinput. electrodesof said modulator t.ube., l 8.-. 'Ihe combination as recited in claim '7 in which the thermionic relay is of the screen grid type and inwhich the screen grid to cathode impedance; of, said- .tube is connected in parallel withzthetanode to cathode impedance of said tube-. J 5

;, G. EMERSON PRAY.

filter network comprisingseries resistance and .t j parallel capacity interposed between said keying 

